Uh... things that seem to work fine in Mongo under light load tend to fall over during heavy load. Things like this problem. Like key reordering: https://jere

Uh... things that seem to work fine in Mongo under light load tend to fall over during heavy load. Things like this problem. Like key reordering: https://jeremywsherman.com/blog/2013/04/23/key-reordering-ruins-mongodb/ https://jeremywsherman.com/blog/2013/04/23/key-reordering-ru... Yes, with enough extremely careful coding knowing exactly all the internals of the database, you can probably avoid these giant gotchas. But that's a hell of a lot of work for a DB that's supposed to be easy. And then you're still dealing with a database without ACID guarantees. No transactions, very little atomicity.... and good luck if your server crashes... we've had multiple customers have their DB corrupted that way. MongoDB is only good for storing data you don't really care about... in which case, why are you bothering to store it at all? What most people end up storing in Mongo: strongly schema'ed, relational data that is critical to their application. This is exactly what mongo is not for.